1. Field of the Invention
The invention relates to the medical techniques for prostheses used in orthopedic surgery, and more particularly to surgical implants for connecting two bone segments and/or for lengthening limbs or of the extremities.
More particularly, the invention relates to an expandable intramedullary nail disposed inside a patient and configured for insertion into a medullary cavity of the patient's limb containing a bone and is designed to be expandable intraoperatively, if desired, by simple assembly and disassembly with an expandable prosthesis engagement instrument.
2. Description of the Prior Art
It is known that after congenital malformations or anomalies, or even after fractures, losses of osseous or other substances, certain bones such as the humerus, femur, tibia, etc., are too short, thus creating asymmetry or hypometry. In the case of lower limbs with slight asymmetry, less than 3 centimeters, orthopedic treatment is called for by adding, for example, a shoe or other orthopedic apparatus to the limb which is short. With asymmetry or hypometry which is more significant, in order to elongate the short limb, surgical solutions currently using two types of means exist:
External fixtures--an operation is performed using external apparatus on certain parts of which, for example, metal pins, etc., go through the soft tissues to reach the bone of which they are an integral part. The apparatus can be seen from outside the limb. The advantage of such apparatus which is therefore accessible from the outside is that a physician can act on the apparatus at determined periods of time in order to consequently provoke a certain degree of elongation of the bone in a progressive manner, generally at the diaphysis of the bone after cutting the latter.
Internal fixtures--the second solution consists of taking action from the inside, i.e., no element can be seen from outside the limb. For this purpose, centromedullary nails or intramedullary nails are generally used or osteosynthesis plates which are suitably fixed to the bone.
The advantage of this solution with respect to the previous one lies in the fact that no element can be seen from outside the limb. On the other hand, the bone cannot be progressively elongated, which may be required for a growing child. However, a quite significant elongation can be carried out thanks to repeated surgical interventions which are consistent each time in obtaining a fixed but limited elongation due to elastic and plastic limits of the soft tissues on stretching. In the case of non-progressive significant elongation, the compensation of the dimensional deviation is risky and requires adjuvants to the osteosynthesis, i.e., grafts, etc., which reduce the mechanical and physiological properties of the elongated bone.
Currently there is no elongatable nail which can be easily assembled and disassembled while still fixed to each bone segment it is aligning.
Various prior art intramedullary nails, and the like, as well as apparatus and method of their construction in general, are known, and exemplary of this prior art are the following patents:
______________________________________ Seppo 3,680,553 Westerhoff 4,157,715 Roalstad 4,262,665 Sivash 4,384,373 Raftopoulos 4,453,539 Moore 4,502,160 Kotz 4,764,171 Kotz 4,892,546 Grammart 5,074,882 Keller EP 0212192 Scales GB 2137884 A Bauman DE 02705154 A1 ______________________________________
The device of Seppo is a fixing apparatus for osteosynthesis of fractures and includes a complex mechanism that does not feature a lengthening function. Westerhoff can be considered as a lengthening device effected solely by means of a small pump which is set out of the cylindrical device. Roalstad does not feature a lengthening function, but is an intramedullary compression device set during the surgical procedure and not capable of being modified thereafter. Raftopoulos discloses an expandable intramedullary device having an expandable part acting as a locker in the bone, and has no lengthening function.